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Preliminary Results of the Beetle Readout for the MaPMTs

Preliminary Results of the Beetle Readout for the MaPMTs. J. Bibby, S. Eisenhardt, F. Muheim, N. Smale. Part 1: as presented on 17.06. Achievements since last LHCb week Common Mode correction Light scan High Voltage scan Conclusion Part 2: new results Calibration

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Preliminary Results of the Beetle Readout for the MaPMTs

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  1. Preliminary Results of theBeetle Readout for the MaPMTs J. Bibby, S. Eisenhardt, F. Muheim, N. Smale Part 1: as presented on 17.06. Achievements since last LHCb week Common Mode correction Light scan High Voltage scan Conclusion Part 2: new results Calibration Measured all connected MaPMT pixels Preliminary analysis of spectra Conclusions Stephan Eisenhardt University of Edinburgh MaPMT workshop, IC, 26.06.2003

  2. Achievements since last LHCb week • New Beetle chip • visible noise factor 2-3 lower compared to the old chip which had died (another sign that the old chip was dodgy…) • Tuning of existing setup: • noise reduction of factor ~2 • Noise reduction session: (2 1/2 days together with John and Nigel) • rerouting of power supplies!! • shielding of LED pulser! • new coax cables between MaPMT and HD board !!!! • new GND routing layout for unused channels at PMT base !!!! • new star point for GND at front-end !!!! • massive (1/2 inch) Al GND plate below HD mother board !!! • all-in-all a noise reduction of factor ~5 • Common mode reduction: • problem:12 connected channels move more than the others • solution: split into different groups and treat independently • noise reduction of factor ~3 • problem: individual channels have ~10% weight  artificial dip at cut position in corrected spectrum • solution:iterative CM reduction  dip reduced and moved to pedestal, CM reduction stays efficient Stephan Eisenhardt

  3. Data Frame from Ntuple w/o CM correction • FED takes 160 samples / event • header samples: • show double peak • also visible on oscilloscope • structure comes from the front-end of the system • 12 channels bonded • 1 analog TestOut • 1 outside the sampled frame due to mismatch in timing • 10 channels visible • bent base line • Beetle1.2 ‘feature’ • signal inverted for better match to FED • gives positive charge signals 128  1 data frame header bits: 200mV bonded channel Stephan Eisenhardt

  4. Signal w/o CM correction • Uncorrected pedestal width:  ~ 4.5 ADC • Double peak structure variable with runs (two peaks, shoulder or broader flank) pedestal run signal run  ~ 2 Stephan Eisenhardt

  5. Signal with CM correction w/o CM correction • Uncorrected pedestal width:  ~ 4.5 ADC • Corrected pedestal width:  ~ 1.4 ADC • artificial dip in spectrum from CM correction on few channels with CM correction  ~ 2 Stephan Eisenhardt

  6. w/o CM correction with CM correction  ~ 2  ~ 1.5 80% signal 65%  ~ 1  < 1 38% 20% LED Light scan • Varied amount of light to determine a working point with:  ~ 1 Stephan Eisenhardt

  7. w/o CM correction with CM correction 750V 775V 800V 825V HV scan I - corner pixel • HV: -750…-825V • Uncorrected pedestal width:  ~ 4.5 ADC • Corrected pedestal width:  ~ 1.4 ADC • clear single photon signal Stephan Eisenhardt

  8. w/o CM correction with CM correction 850V 875V 900V 925V HV scan II - corner pixel • HV: -850…-925V • Uncorrected pedestal width:  ~ 4.5 ADC • Corrected pedestal width:  ~ 1.4 ADC • clear single photon signal Stephan Eisenhardt

  9. w/o CM correction with CM correction 750V 800V 850V 900V HV scan - center pixel • HV: -750…-900V • this pixel has a significantly higher gain Stephan Eisenhardt

  10. Things to do: • calibration of signal done • proper S/N calculation done • straighten out shifts in timing done • check LED pulse width with analog TestOut channel not done • get proper BoardBeetle due to be submitted • the whole issue about digital readout is not yet touched... still Stephan Eisenhardt

  11. Part 1: Conclusions • Great progress since last LHCb week • level of noise using the HD board is down by 2 orders of magnitude • setup much better understood • this knowledge is put into the design of the BoardBeetle • analog readout of 8-stage MaPMT with Beetle1.2 is possible • proper S/N figure still to be determined • Binary readout option (no CM correction) still to be evaluated with BoardBeetle • Readout of 12-stage MaPMT with Beetle1.2MA0 (Nigel) looks very promising as well  report at MaPMT workshop • a great ‘Thank you!’ to John and Nigel! Stephan Eisenhardt

  12. individual Gauss fits no CM correction! 12 runs with varied voltage step Polynom fit to peak positions Beetle Readout Calibration • Voltage step: 0.0V,0.5V,…5.0V,5.5 • Error: 0.025V… 0.2V • Rise time: <10ns • Ringing: within 25ns • Attenuation: 400 10 • Ceff: 3.0 0.1pC • 1V: Q = CV = 472.3 ke- = ~150mV • 1 photoelectron • Linear description up to 2.5V (2.5 photons) • Quadratic description beyond Stephan Eisenhardt

  13. Signal in Low Gain Pixel • Poisson fit: • No photo conversion at 1st dynode included • Shoulder not described • Gain underestimated •  = 0.6 • @ 800V (850V): • Gain = 26 (37) • Noise = 1.2 (1.2) • S/N = 22 (31) • K1 = 3.5 (3.4) • Signal loss: ~13% (~10%) Stephan Eisenhardt

  14. Signal in High Gain Pixel • Poisson fit: • No photo conversion at 1st dynode included • Shoulder not described • Gain underestimated •  = 0.6 • @ 800V (850V): • Gain = 51 (78) • Noise = 1.6 (1.6) • S/N = 33 (50) • K1 = 3.5 (4.6) • Signal loss: ~9% (~7%) Stephan Eisenhardt

  15. Noise Status • where are we: • CM correction gives factor of ~3 reduction • then we get a pedestal width of 1…1.5ADC channels • calibration gives a noise level of 2000…3000 e- • that is a factor 2…3 larger than what we expect for a channel with 10pF • where can we get with BoardBeetle: • track lengths 25…75mm (instead of ~175mm + two connectors) • all channels connected (no bricolage to care about unused channels) • less antennas • low impedance ground • lower capacity • great care taken to avoid noise brought in from the outside (e.g. via supplies, grounds or fast control) • with that there is reasonable hope to get a noise level of O(1000 e-) without CM correction Stephan Eisenhardt

  16. Room for Improvement • with the HD system: • Improve fits • Try to understand shoulder (real photo conversion at dynode??) • Comparison with Beetle1.2MA0 and 12-stage MaPMT • Trial run of Binary operation (noise still a factor of 3…6 too high) • with the BoardBeetle: • Improved noise situation • Full MaPMT readout • Serious evaluation of binary readout • Test beam Stephan Eisenhardt

  17. Things to do: • study LED pulse behaviour through analog TestOut channel • get proper BoardBeetle, cabeling and jigs and get it operational • compare results from HD board to BoardBeetle to see what we gained • compareBeetle1.2(8-dyn) and Beetle1.2(12-dyn) • get through the learning curve of the digital readout Stephan Eisenhardt

  18. Part 2: Conclusions • Calibration: linear up to 2.5 photons, quadratic behaviour beyond 150mV/47ke- or 26ADC/47ke- • Noise level: 2000…3000 e- • Still room for improvement and reason to get it with BoardBeetle • Present Poisson fit underestimates gain: but we already get: • @800V: • Gain: 26…51ADC • S/N: 22…33 • Signal loss: 13…9% • @850V: • Gain: 37…78ADC • S/N: 31…50 • Signal loss: 10…7% • That already looks very nice! • This promises to get an exciting test beam! • Do I have to mention that there still is lots of work to be done? Stephan Eisenhardt

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